In the case of certain types of work machines such as skid steer loaders, wheel loaders, backhoe loaders and track loaders, attachments or tools such as an auger, sweeper, grapple, backhoe and the like are often times pivotally mounted to the implement lift arm assembly by cooperatively engageable mounting means associated with both the lift arm assembly and the particular attachment or tool. These attachments or tools typically include their own hydraulic motor or actuator to drive and operate the various functions associated with that particular tool or attachment. One hydraulic system, which typically includes an implement hydraulic pump as well as lift and/or tilt cylinders, is used to actuate and control the implement lift and/or tilt mechanisms, which lift and/or tilt mechanisms are commonly referred to as the implement control system. A second and separate hydraulic system, typically referred to as the auxiliary hydraulic system, is used to control the flow of hydraulic fluid between the implement hydraulic pump and the hydraulic motor or actuator associated with the attachment or tool to actuate and control the operation thereof. The flow of hydraulic fluid to the hydraulic motor or actuator associated with the particular attachment or tool is typically controlled through actuation of some type of an auxiliary valve.
Many different types of auxiliary hydraulic control systems are known and utilized including auxiliary hydraulic systems which are electrically controlled through the use of a plurality of switches located in the operator compartment. Often times, the known auxiliary hydraulic control systems include a mode select switch to prevent inadvertent actuation of the continuous flow function as well as different types of pressure relief means and diverter valves which are included within the auxiliary hydraulic circuit to further control the operation thereof. Such known systems typically provide continuous flow in the auxiliary hydraulic circuit in one direction only when a latching switch is activated. See, for example, the electrically controlled auxiliary hydraulic system for a skid steer loader disclosed in U.S. Pat. No. 4,949,805. Still other known auxiliary hydraulic systems are mechanically actuated through a system of control levers, one or more hydraulic control valves, and mechanical linkage.
Often times, depending upon the particular attachment or tool and the particular application or task being performed by such attachment or tool, full hydraulic flow to the particular attachment or tool is not always necessary. In fact, under certain operating conditions, less than full or maximum flow provided by the auxiliary circuit is desirable. This is not always possible with the known systems and, as a result, auxiliary hydraulic system flow rates often times exceed the task requirements. Still further, there are likewise situations where continuous flow to a particular attachment or tool in an opposite or reverse direction is also desirable. Here again, this is not possible with the known systems.
It is therefore desirable to provide an auxiliary hydraulic control system which reduces system components and which eliminates the need for a mode select switch and/or an on-off switch for operation of the auxiliary system. It is also desirable to provide an auxiliary hydraulic control system which will allow for continuous flow in both the forward and reverse directions and which will provide for latching or otherwise allowing the continuous flow command to be set at a flow rate which can be any percentage or scaling of the maximum flow rate available in the selected direction.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.